DESCRIPTION: For the first time in history, people with a lower limb amputation have regained normative function during level-ground walking due to the development of a new powered ankle-foot prosthesis. However, negotiating natural and built environments also requires the ability to walk and run on uphill and downhill slopes. Thus, an ankle-foot prosthesis must be able to accomodate changes in velocity and slope to allow Veterans with a leg amputation to achieve full functional equivalence during locomotion. The proposed Career Development Award aims to characterize biological ankle joint function during walking and running on slopes in order to further develop advanced powered ankle-foot prostheses. Ankle joint torque and angle data will be collected from 20 non-amputees while walking and running at multiple velocities (1.0, 1.25, 1.5, 2.0, 2.5, and 3.0 m/s) on level, uphill, and downhill slopes (0?, +/-3?, +/-6?, and +/-9?). This biological ankle joint data will be used to develop prosthetic ankle joint control parameters for a powered ankle-foot prosthesis at each velocity and slope combination. Then, these parameters will be implemented and tested in the powered prosthesis. Ankle joint torque and angle, muscle activity, and metabolic cost data will be collected from 10 people with a unilateral transtibial amputation using the powered prosthesis while walking and running at the above- mentioned velocity and slope combinations. This data will be compared to that of non-amputees to determine if a powered prosthesis is capable of emulating a biological ankle joint. It is predicted that if biologically- equivalent mechanical power, compliance, and range of motion are supplied by the prosthetic ankle joint, people with a lower limb amputation will achieve equivalent biomechanics, muscle activity, and metabolic energy costs compared to non-amputees. The data from the proposed CDA-2 will be highly valuable for use in the design of prostheses, and also in the design of orthoses and other assistive devices. With the increasing number of Veterans with leg amputations, there is a heightened demand for advanced prostheses. The proposed research and development of a state-of-the-art powered prosthesis specifically aims to give people with a lower limb amputation the ability to walk and run over a full range of velocities on level-ground, uphill, and downhill slopes. I am committed to improving Veterans' rehabilitation and healthcare through ongoing research, development, and analysis of assistive mechanical devices. My previous research experience, in the areas of human biomechanics, physiology, and mechatronics, and my CDA-1, entitled the Effects of wearing a powered ankle-foot prosthesis on amputee walking, have addressed questions directly related to the proposed research. The current proposal, to comprehensively study uphill and downhill locomotion, has specific relevance to Veterans because advanced mechanical devices promise to significantly improve function and indirectly improve quality of life. I plan to continue pursung my research career and aspire to become an independent investigator within the Department of Veterans Affairs Research Rehabilitation and Development Service. To further my career aspirations, I have proposed professional goals to expand my scientific research skills and knowledge, knowledge of musculoskeletal modeling and control systems techniques, and clinical knowledge and application of prosthetic devices. I also bring together mentors, consultants, and collaborators with extensive expertise in prosthesis design and development, rehabilitation, computer modeling and simulation, and the biomechanics and energetics of human locomotion; areas that will contribute significantly toward my career development and toward the goals of my research. I am very excited about the proposed project and look forward to this important work.